Interacting with the real world can be accomplished in various ways. At one extreme, a person can interact with it directly (e.g., push a door to open it). At another extreme, a person can interact with the real world through various levels of indirection such as with a control panel or a software program. Although direction interaction with the real world is probably the most intuitive way for a person to affect changes, sometimes such interaction is not possible due to dangerous conditions (e.g., manipulation of nuclear fuel), problems of scale (e.g., manipulation of the interior of a single cell organism), and problems of distance (e.g., teleconferencing).
Teleconferencing over the Internet is increasingly popular for many applications, such as distance learning. Through remote participation, students can attend classes from their dorm rooms, scientists can participate in seminars held in other countries, and executives can discuss critical issues without leaving their offices. There are many ways to support such activities: one-way audio broadcast, two-way audio communication, and two-way video communication. However, each is limited in the amount of intuitive interaction afforded to the participants.